Starbucks staff in New York City were so rude to deaf customers they mocked them and called the police to try to get them kicked out, a lawsuit says.

The lawsuit seeks unspecified damages and an order from the court to stop discriminatory behaviour for what is described as multiple occasions of abuse over the past year.

The suit, filed in federal court in Manhattan on behalf of 12 people, says one Starbucks employee laughed hysterically at a plaintiff's speech while others objected to a monthly meeting of a group of deaf people named Deaf Chat Coffee and called police.

Starbucks spokeswoman Jamie Riley said the Seattle-based company, which refers to its employees as partners, is investigating.

"Discrimination of any kind at Starbucks in unacceptable," she said. "We take these allegations very seriously and believe that they are neither in line with our values nor our track record of engaging the deaf community as partners and as customers."

The lawsuit said the police were called to a Starbucks store at Astor Place in lower Manhattan on March 7 after more than 10 people, some of whom bought coffee and pastries, gathered for the monthly meeting.

According to the lawsuit, those participating in the meeting were "shocked and frightened" when police responded to a report of a disturbance, a meeting being conducted without a permit and a claim that most deaf people at the store were not paying customers.

The police officers found no illegal conduct and apologised to the plaintiffs before reprimanding Starbucks employees for calling them, the lawsuit said.

The plaintiffs had suffered humiliation, embarrassment and emotional pain and suffering as a result of the Starbucks employees' actions, it said.